Work around a clang/win bug, add a .h file to gyp/gn files.

media/base/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//media/media_options.gni")
@@ skipping 45 matching lines @@
     "bit_reader.h",
     "bit_reader_core.cc",
     "bit_reader_core.h",
     "bitstream_buffer.h",
     "buffering_state.h",
     "buffers.h",
     "byte_queue.cc",
     "byte_queue.h",
     "cdm_callback_promise.cc",
     "cdm_callback_promise.h",
+    "cdm_config.h",
     "cdm_context.cc",
     "cdm_context.h",
     "cdm_factory.cc",
     "cdm_factory.h",
     "cdm_key_information.cc",
     "cdm_key_information.h",
     "cdm_promise.cc",
     "cdm_promise.h",
     "cdm_promise_adapter.cc",
     "cdm_promise_adapter.h",
@@ skipping 455 matching lines @@
       if (is_posix) {
         yasm_flags += [ "-DELF" ]
         if (current_cpu == "x64") {
           # TODO(ajwong): Why isn't this true in mac?
           yasm_flags += [ "-DPIC" ]
         }
       }
     }
   }
 }